Fabrication And Sensing Properties Of Tapered Microfiber

Optical fiber sensor has unique advantages,such as light weight,small size,flexible,anti-corrosion and heat resistance,fast response speed,and can provide multiple or distributed sensing.At present it has been used in physics,chemistry,biology and other fields,the information such as magnetic field,electric field,temperature,humidity,sound field,liquid level,current,biological molecules,chemical material parameters of testing and research.In this era of rapid development of information,optical fiber sensing technology is also constantly innovating.Various new sensors can be fabricated by micromachining the optical fiber,and their sensitivity can also be improved.Magnetic fluid(MF)is a new kind of functional material,which has the fluidity of liquid,the magnetism of solid magnetic material,and the characteristics of magnetotunable refractive index,tunable transmission and Faraday effect.MF has been widely used in optical fiber magnetic field sensor,optical fiber temperature sensor and so on.Because the MF is sensitive to both magnetic field and temperature,the cross-sensitivity of magnetic field and temperature needs to be considered in the measurement of magnetic field by the fiber optic sensor based on MF.In this paper,a composite fiber sensing structure of a NTF cascaded FBG is proposed and studied.Because FBG is sensitive to temperature and insensitive to magnetic field,the problem of magnetic field-temperature cross sensitivity can be solved with FBG.NTF is essentially a kind of MZ interferometer structure.The experiment can measure temperature and magnetic field simultaneously by monitoring the transmission spectra of FBG and MZ interference.The experimental results show that in the range of 0-18 m T and 25-50 ℃,the NTF with an interference arm length of 3 mm has the maximum magnetic field sensitivity and temperature sensitivity,which are 1.159 nm/m T and-1.737nm/℃,respectively.When the NTF’s waist diameter is fixed,the sensitivity can be improved by shortening the length of the interference arm.The sensor structure has the advantages of simplicity,low cost and convenient fabrication.The paper also presents a kind of sensing structure of cupped taper cascaded coreoffset fiber,which is essentially a kind of fiber MZ interferometer.The temperature and refractive index sensing characteristics of the structure are studied.The experimental results show that the maximum temperature sensitivity is 0.070 nm/℃ when the length of the interference arm is 12 mm.The maximum refractive index sensitivity is 29.895nm/RIU in the refractive index range of 1.330-1.429.The proposed sensor structure has the characteristics of easy fabrication,simple structure and low cost.